Itisnotasecret61.　　　　treesarevitaltoourlife.Theyprovide...

问题详情：

It is not a secret 61.　　　　trees are vital to our life. They provide us with food, wood and most 62.　　　　 (important), oxygen. Now there is one more thing we can add to this list—blocking out harmful bacteria from water. 

The discovery 63. 　　　　(make) by a team 64. 　　　　(consist) of scientists from  the  Massachusetts  Institute  of  Technology (MIT)  and high school students

65.　　　　 were seeking a natural water filter(过滤)—one that would help communities in developing countries that do not have 66.　　　　 (accessible) to modern water filter systems. 

The 67.　　　　 (research), led by Professor Rohit Karnik, decided to turn68._______ trees for help, because they could allow liquid to flow through, while blocking out air bubbles. 

They began by cutting 1.5-inch-wide sections of tree bark from the branches of a white pine tree. The people related then tested the wood’s filtering ability by pouring water containing red dye particles of different sizes through. To their 69.　　　　 (amaze), they found that it was effective in trapping all the particles. Greatly 70.　　　　 (encourage), the team conducted another experiment, this time with water that contained bacteria. Sure enough, the sapwood held back 99% of the bacteria, allowing only 1% to flow through. 

【回答】

61. that   

62. importantly   

63. was made   

64. consisting   

65. who/that

66. access 

67. researchers   

68. to         

69. amazement    

70. encouraged 

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